How to use the pyinstaller.buildtests.basic.test_threading2.TestThreadClass.start function in pyinstaller

_OUT_EXPECTED = ['ONE', 'TWO', 'THREE']


# Code for the subprocess.
if 'PYI_THREAD_TEST_CASE' in os.environ:
    class TestThreadClass(threading.Thread):
        def __init__(self):
            threading.Thread.__init__(self)

        def run(self):
            print 'ONE'
            print 'TWO'
            print 'THREE'
    # Main process should not exit before the thread stops.
    # This is the behaviour of Python interpreter.
    TestThreadClass().start()


# Execute itself in a subprocess.
else:
    # Differenciate subprocess code.
    itself = sys.argv[0]
    # Run subprocess.
    try:
        import subprocess
        proc = subprocess.Popen([itself], stdout=subprocess.PIPE,
                env={'PYI_THREAD_TEST_CASE': 'any_string'},
                stderr=subprocess.PIPE, shell=False)
        # Waits for subprocess to complete.
        out, err = proc.communicate()
    except ImportError:
        # Python 2.3 does not have subprocess module.